Electrodes#

How to describe an electrode: the design as an electrode spec (composition, route, design values), a physical coated disc or batch as an electrode instance.

kind names the active material, from the same curated vocabulary as powders; a non-active kind warns but saves.
The spec is the coated design (composition, route, design values); the electrode instance is a physical disc or batch.
active_material_spec_id cites the powder product, so a design never points at a bare vocabulary key.
polarity is authored or absent; half and three-electrode cells name electrodes by role instead (see half cells).

Define one#

An electrode spec (the design)#

Python

from battinfo.api import create_electrode_spec

record = create_electrode_spec(
    uid="kxwy-5f5f-f682-hhch",
    name="NMC811 cathode design A",
    active_material_kind="nmc811",     # from the curated material-kind vocabulary
    active_material_spec_id="https://w3id.org/battinfo/spec/7d9k-2m4p-8t3x-6nq5",
    composition={"active": 0.96,       # weight fractions -> coating.component
                 "binder": {"name": "PVDF", "fraction": 0.02},
                 "conductive_additive": {"name": "Carbon black", "fraction": 0.02}},
    coating={"double_sided": False},   # coated on one side (a lab half-cell disc)
    source_type="lab",
)

Canonical record

{
  "schema_version": "0.2.0",
  "electrode_spec": {
    "id": "https://w3id.org/battinfo/spec/kxwy-5f5f-f682-hhch",
    "short_id": "kxwy5f",
    "name": "NMC811 cathode design A",
    "active_material_kind": "nmc811",
    "active_material_spec_id": "https://w3id.org/battinfo/spec/7d9k-2m4p-8t3x-6nq5",
    "coating": {
      "component": {
        "active_material": [
          {
            "name": "NMC811 (LiNi0.8Mn0.1Co0.1O2)",
            "property": {
              "mass_fraction": {
                "value": 0.96,
                "unit": "1"
              }
            },
            "material_spec_id": "https://w3id.org/battinfo/spec/7d9k-2m4p-8t3x-6nq5"
          }
        ],
        "binder": [
          {
            "name": "PVDF",
            "property": {
              "mass_fraction": {
                "value": 0.02,
                "unit": "1"
              }
            }
          }
        ],
        "additive": [
          {
            "name": "Carbon black",
            "property": {
              "mass_fraction": {
                "value": 0.02,
                "unit": "1"
              }
            }
          }
        ]
      },
      "double_sided": false
    }
  },
  "provenance": {
    "source_type": "lab",
    "retrieved_at": 1750000000,
    "battinfo_version": "0.7.0"
  }
}

JSON-LD

Emitted by record_to_jsonld, hosted-context mode.

{
  "@context": [
    "https://w3id.org/emmo/domain/battery/context",
    {
      "schema": "https://schema.org/",
      "dcterms": "http://purl.org/dc/terms/",
      "battinfo": "https://w3id.org/battinfo/"
    }
  ],
  "@type": [
    "Description",
    "schema:ProductModel",
    "schema:CreativeWork"
  ],
  "isDescriptionFor": {
    "@type": "LithiumNickelManganeseCobaltOxideElectrode",
    "hasCoating": {
      "@type": "ElectrodeCoating",
      "hasActiveMaterial": {
        "@type": "ActiveMaterial",
        "schema:name": "NMC811 (LiNi0.8Mn0.1Co0.1O2)",
        "schema:isVariantOf": {
          "@id": "https://w3id.org/battinfo/spec/7d9k-2m4p-8t3x-6nq5"
        },
        "hasProperty": {
          "@type": [
            "MassFraction",
            "ConventionalProperty"
          ],
          "hasNumericalPart": {
            "@type": "RealData",
            "hasNumberValue": 0.96
          },
          "hasMeasurementUnit": "https://w3id.org/emmo#EMMO_5ebd5e01_0ed3_49a2_a30d_cd05cbe72978"
        }
      },
      "hasBinder": {
        "@type": [
          "PolyvinylideneFluoride",
          "Binder"
        ],
        "schema:name": "PVDF",
        "hasProperty": {
          "@type": [
            "MassFraction",
            "ConventionalProperty"
          ],
          "hasNumericalPart": {
            "@type": "RealData",
            "hasNumberValue": 0.02
          },
          "hasMeasurementUnit": "https://w3id.org/emmo#EMMO_5ebd5e01_0ed3_49a2_a30d_cd05cbe72978"
        }
      },
      "hasConductiveAdditive": {
        "@type": [
          "CarbonBlack",
          "ConductiveAdditive"
        ],
        "schema:name": "Carbon black",
        "hasProperty": {
          "@type": [
            "MassFraction",
            "ConventionalProperty"
          ],
          "hasNumericalPart": {
            "@type": "RealData",
            "hasNumberValue": 0.02
          },
          "hasMeasurementUnit": "https://w3id.org/emmo#EMMO_5ebd5e01_0ed3_49a2_a30d_cd05cbe72978"
        }
      },
      "schema:additionalProperty": {
        "@type": "schema:PropertyValue",
        "schema:name": "double_sided",
        "schema:value": false
      }
    },
    "hasActiveMaterial": {
      "@id": "https://w3id.org/battinfo/spec/7d9k-2m4p-8t3x-6nq5#described",
      "@type": "ActiveMaterial"
    },
    "skos:prefLabel": "NMC811 cathode design A",
    "@id": "https://w3id.org/battinfo/spec/kxwy-5f5f-f682-hhch#described"
  },
  "@id": "https://w3id.org/battinfo/spec/kxwy-5f5f-f682-hhch",
  "schema:name": "NMC811 cathode design A"
}

What to notice:

active_material_spec_id cites the powder, so no design points at a bare vocabulary key.

An electrode (the disc in one cell)#

Python

from battinfo.api import create_electrode

record = create_electrode(
    uid="3w87-0ddf-ryjg-evxe",
    name="Cathode disc 07, cell LAB-2026-0001",
    spec_id="https://w3id.org/battinfo/spec/kxwy-5f5f-f682-hhch",
    # Genealogy: the coated strip this disc was punched from is itself an
    # electrode record; siblings cut from it share the same parent.
    parent_id="https://w3id.org/battinfo/electrode/9m2k-4tqv-7xw3-1nfh",
    piece_id="disc-07",
    source_type="lab",
)

Canonical record

{
  "schema_version": "0.2.0",
  "electrode": {
    "id": "https://w3id.org/battinfo/electrode/3w87-0ddf-ryjg-evxe",
    "electrode_spec_id": "https://w3id.org/battinfo/spec/kxwy-5f5f-f682-hhch",
    "short_id": "3w870d",
    "name": "Cathode disc 07, cell LAB-2026-0001",
    "parent_id": "https://w3id.org/battinfo/electrode/7d9k-2m4p-8t3x-6nq5",
    "piece_id": "disc-07"
  },
  "provenance": {
    "source_type": "lab",
    "retrieved_at": 1750000000,
    "battinfo_version": "0.7.0"
  }
}

JSON-LD

Emitted by record_to_jsonld, hosted-context mode.

{
  "@context": [
    "https://w3id.org/emmo/domain/battery/context",
    {
      "schema": "https://schema.org/",
      "dcterms": "http://purl.org/dc/terms/",
      "battinfo": "https://w3id.org/battinfo/"
    }
  ],
  "@type": "Electrode",
  "@id": "https://w3id.org/battinfo/electrode/3w87-0ddf-ryjg-evxe",
  "schema:name": "Cathode disc 07, cell LAB-2026-0001",
  "schema:isVariantOf": {
    "@id": "https://w3id.org/battinfo/spec/kxwy-5f5f-f682-hhch"
  },
  "prov:wasDerivedFrom": {
    "@id": "https://w3id.org/battinfo/electrode/7d9k-2m4p-8t3x-6nq5"
  },
  "schema:identifier": {
    "@type": "schema:PropertyValue",
    "schema:name": "piece_id",
    "schema:value": "disc-07"
  }
}

What to notice:

electrode_spec_id carries the design; a cell instance points at this disc through working_electrode_id.

Fields#

Generated from the packaged JSON Schemas — the same files battinfo validate and the registry’s publish gate enforce. Every record also carries the shared envelope (schema_version, provenance, and optional notes, funding, contributor, license). Quantities are {value, unit} maps and may also carry value_basis (Measured, Conventional, Rated, or Nominal) and conditions (the parameters under which the value holds, each itself a quantity; a qualitative condition may be value_text alone). In JSON-LD, conditions ride a measurement node the quantity isOutputOf; the voltage_reference key instead becomes a hasMetrologicalReference datum on the quantity, beside its unit. When authoring, an instance references its spec with the spec_id= kwarg; the record stores the self-describing <type>_spec_id key shown in the tables below.

electrode-spec fields#

Schema: electrode-spec.schema.json · required at top level: schema_version, electrode_spec, provenance

Field	Type	Required	Description
`id`	→ ComponentSpecIri	yes
`short_id`	→ ShortId
`name`	string	yes	Human-readable electrode name / designation (e.g. ‘Si-Gr anode, aqueous’, ‘NMC811 cathode 96/2/2’).
`active_material_kind`	string		Required Level-1 kind naming the ACTIVE material of this electrode, from the curated material-kind vocabulary (e.g. ‘graphite’, ‘silicon_graphite’, ‘nmc811’, ‘lfp’). Named for what it identifies: the electrode’s active material, not the electrode’s form. Required so a purchased electrode whose powder provenance is unknown is still queryable on the same aggregation axis as one built from an authored material-spec. Aliases resolve on input; an unknown kind is rejected at save time. See battinfo.electrodes.electrode_kind_keys().
`kind`	string		Deprecated alias of active_material_kind; accepted so existing records keep validating, normalized to active_material_kind on round-trip.
`polarity`	`positive` \| `negative` \| `unknown`		Electrode polarity, authored when the design has a side to state. Never derived from the kind: which side an active material sits on is system-relative (graphite is the positive electrode of a lithium-counter half cell). Role-based cells (half / three-electrode) name electrodes by role instead.
`grade`	string		Producer grade / design version (e.g. ‘v2’, ‘rev B’). Part of spec identity together with the producer and the electrode name.
`active_material_spec_id`	→ MaterialSpecIri		Optional canonical IRI of the material-spec for this electrode’s active material, present when the powder is known and authored. Absent for a purchased electrode of known chemistry but unknown powder — ‘kind’ still carries the chemistry.
`material`	→ material-component		The electrode body as a single monolithic material - an uncoated metal foil or disc (lithium metal counter, zinc foil). States the material directly; there is no coating and no separate current collector, the foil is both. Alternative to `coating` for uncoated electrodes.
`coating`	→ electrode-coating		Coating composition and coating-level design values. ‘component.active_material / binder / additive’ each carry a weight fraction under property.mass_fraction — the same shape a cell-spec’s inline electrode coating uses, so a composition authored here is the composition a cell reads.
`current_collector`	→ current-collector		Current-collector foil: material (name and/or material_spec_id) and its thickness under property.
`tab`	→ tab		Electrode current-collector tab: material plus its dimensions (width, thickness, length, weld_width, tape_width) under property.
`processing`	→ Processing
`manufacturer`	→ OrgRef		Producer of this electrode design — a vendor for a purchased electrode, or the lab that designed it for an in-house coating. Part of spec identity.
`supplier`	→ OrgRef		Supplier or vendor the item was sourced from.
`product_id`	string		Producer product / design identifier. Preferred over ‘name’ as the product half of the spec identity when present.
`property`	→ quantitative-properties		Electrode-level design values: areal loading (‘loading’), dry and calendered coating thickness (‘dry_thickness’ / ‘calendered_thickness’), nominal areal capacity (‘areal_capacity’), porosity, diameter / width / length. An open snake_case map — new design values need no schema change.
`description`	string
`comment`	string		Free-text comment.

electrode fields#

Schema: electrode.schema.json · required at top level: schema_version, electrode, provenance

Field	Type	Required	Description
`id`	→ ComponentIri	yes
`electrode_spec_id`	→ ComponentSpecIri	yes	Canonical IRI of the electrode-spec this batch realizes. Required: a built electrode without a design is not describable.
`short_id`	→ ShortId
`name`	string		Human-readable label for this batch.
`lot_id`	string		Producer / supplier lot number for a purchased electrode.
`parent_id`	→ ComponentIri		Canonical IRI of the electrode this piece was cut from - the coated roll, web, or strip its siblings share. The parent is itself an electrode record (usually realizing the same spec), so genealogy chains compose: cell -> disc -> parent roll -> electrode-spec.
`piece_id`	string		Label of this cut piece within its parent (e.g. ‘disc-07’, ‘strip-B’). Joins the identity seed, so pieces cut from the same parent mint distinct IRIs.
`batch_id`	string		Coating batch label (e.g. ‘Si-AQ-1’). Together with the spec IRI this is the batch’s identity — the IRI is minted from the pair.
`supplier`	→ OrgRef		Supplier or vendor the item was sourced from.
`manufactured_at`	→ FlexDate		Date this batch was coated / built.
`received_date`	→ FlexDate		Date a purchased batch was received.
`expires_at`	→ FlexDate
`amount`	→ quantity		Quantity of this batch on hand or consumed (e.g. coated area in cm2, web length in m, mass in g).
`count`	integer		Number of discrete pieces in this batch (e.g. punched discs).
`storage`	string		Storage conditions for this batch (e.g. ‘argon glovebox’, ‘dry room, -40 degC dew point’).
`datasets`	array of → DatasetLink		Characterization datasets for this batch (thickness maps, SEM, adhesion, half-cell checks, …).
`property`	→ quantitative-properties		As-built batch actuals — measured loading, measured calendered thickness, measured porosity, disc diameter, disc mass. An open snake_case map: whatever this batch was actually measured for is recordable without a schema change.
`comment`	string		Free-text comment.

Design notes#

The reasoning behind the model

Design vs disc. The spec is the design: composition (coating.component with active/binder/additive holders), processing route, design values, and batch statistics stated with the structured standard_deviation / sample_count fields. The instance is the physical disc or batch — the per-cell as-built figures (mass, loading, areal capacity) live here, because they were true before any test ran.

Genealogy: pieces are cut from a parent. A coating run makes one big source — a roll in a factory, a strip in the lab — and the electrodes that reach cells are cut from it. Both are electrode records: the parent carries the batch facts (batch_id, count, amount, batch statistics), and each cut piece states parent_id (the record it was cut from) and piece_id (its label within the parent, e.g. disc-07, which joins the identity seed so siblings mint distinct IRIs). Chains compose — roll → sheet → disc is two hops of the same relation — and each hop emits as prov:wasDerivedFrom, so the full lineage cell → disc → roll → electrode-spec → material-spec is walkable in the graph.

Half cells name their electrodes by role, not by polarity. A half cell has no sides to name, and in the working-electrode convention a graphite working electrode charges toward 1 V vs Li/Li+ — polarity labels would mislead. polarity is therefore authored or absent, never derived from the kind: an “LFP negative electrode” is a legitimate design (lithium-counter half cell), not a typo, and nothing warns about it.

Cells reference electrodes. Which electrode pair a cell uses follows from its cell_configuration — the polarity holders (positive_electrode / negative_electrode) for a full cell, the role holders (working_electrode / counter_electrode) for a half or three-electrode cell. A cell instance points at the physical disc inside it through working_electrode_id.

Tabs and coatings belong to the electrode. A current-collector tab (Electrode.tab) carries identity fields plus a property dict (width, thickness, weld width) and emits under hasCurrentCollectorTab. A coating carries the composition, its own properties, and double_sided — whether the current collector is coated on both sides or one; a secondary layer such as a ceramic coating is simply an additional coating holder.

The active material is named for what it is. active_material_kind names the electrode’s active material from the curated material-kind vocabulary — not kind, which on an electrode would read as its form (porous, foil, rotating-disc). The old kind spelling stays accepted as a deprecated alias and normalizes on round-trip.

Emission. The spec is an information artifact: it emits typed [Description, schema:ProductModel, schema:CreativeWork] — EMMO’s Description is the very class BatterySpecification subclasses, so the spec sits in the right family until an ElectrodeSpecification class is published (on the upstream ask list) — and its isDescriptionFor node carries the physical typing: the chemistry electrode class derived from active_material_kind (GraphiteElectrode, LithiumIronPhosphateElectrode, …), with an authored polarity stacking PositiveElectrode / NegativeElectrode on top. Role holders emit role types (WorkingElectrode, and the counter of a two-electrode half cell types as both CounterElectrode and ReferenceElectrode).